System for cooling multiple logic molecules

ABSTRACT

An exemplary embodiment is a cooling system for cooling multiple logic modules. The cooling system includes a condenser, a first electrically controlled expansion valve coupled to the condenser and a first evaporator coupled to the first electrically controlled expansion valve. A second electrically controlled expansion valve is coupled to the condenser and a second evaporator coupled to the second electrically controlled expansion valve. A controller provides control signals to the first electrically controlled expansion valve and the second electrically controlled expansion valve to control operation of the first electrically controlled expansion valve and the second electrically controlled expansion valve. A compressor is coupled to the first evaporator, the second evaporator and the condenser.

FIELD OF THE INVENTION

The present invention relates generally to cooling systems and inparticular to a cooling system for cooling multiple logic modules.

BACKGROUND OF THE INVENTION

One of the factors that limit processing speed in computer systems isthe generation of excessive heat at higher clock speeds. Significantgains of speed and reliability have been achieved by cooling logicmodules. Cooling multiple logic modules with different heat loads to thesame temperature with a single refrigeration system is a difficult task.The problem stems from the common source and sink that a singlecompressor/condenser provides. Various attempted solutions to thisproblem include using speed control, separate TX valves for theevaporator and hot gas mixing independently with each inlet. Theseapproaches have been inadequate.

SUMMARY OF THE INVENTION

An exemplary embodiment is a cooling system for cooling multiple logicmodules. The cooling system includes a condenser, a first electricallycontrolled expansion valve coupled to the condenser and a firstevaporator coupled to the first electrically controlled expansion valve.A second electrically controlled expansion valve is coupled to thecondenser and a second evaporator is coupled to the second electricallycontrolled expansion valve. A controller provides control signals to thefirst electrically controlled expansion valve and the secondelectrically controlled expansion valve to control operation of thefirst electrically controlled expansion valve and the secondelectrically controlled expansion valve. A compressor is coupled to thefirst evaporator, the second evaporator and the condenser.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a cooling system in an exemplary embodiment of theinvention.

FIG. 2 depicts a cooling system in another exemplary embodiment of theinvention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 depicts a cooling system 100 in an exemplary embodiment of theinvention. Cooling system 100 includes a condenser 104 and twoevaporators 106 and 108. Evaporators 106 and 108 cool logic modules 110and 112, respectively. Logic modules 110 and 112 are multi-chip modules(MCMs) but it is understood that other logic modules (e.g., singleprocessors, memory) may be cooled. As used herein, logic modules isintended to include a variety of electrical components.

Both evaporators 106 and 108 are supplied refrigerant from a commoncondenser 104. An expansion valve 114 receives high pressure liquidrefrigerant from condenser 104 and generates low pressure liquidrefrigerant to evaporator 106. An expansion valve 116 receives highpressure liquid refrigerant from condenser 104 and generates lowpressure liquid refrigerant to evaporator 108. Expansion valves 114 and116 are electrically controllable. A controller 120 provides controlsignals to expansion valve 114 and expansion valve 116 to controlrefrigerant flow and pressure drop across each expansion valve. In anexemplary embodiment, expansion valves 114 and 116 includes a steppermotor the responds to control signals from controller 120. The steppermotor opens or closes an orifice in the expansion valve to regulaterefrigerant flow and pressure drop. Controller 120 executes a computerprogram to control the expansion valves 114 and 116.

The low pressure liquid refrigerant exits expansion valves 114 and 116and is supplied to evaporators 106 and 108, respectively. Therefrigerant in each evaporator 106 and 108 is converted to low pressurevapor refrigerant and provided to a common compressor 122. High pressurevapor from compressor 122 is supplied to condenser 104. Fan 126establishes air flow across condenser 104 to facilitate cooling the highpressure vapor refrigerant to high pressure liquid refrigerant.

A plurality of temperature sensors are distributed throughout thecooling system 100. The sensors may be thermistors or other knowntemperature sensors. Sensor T1 measures air temperature enteringcondenser 104. Sensor T2 measures air temperature exiting condenser 104.Sensors T3 and T3′ provide redundant measurement of refrigeranttemperature exiting condenser 104. Sensor T4 measures refrigeranttemperature entering condenser 104. Sensor T6 measures refrigeranttemperature entering evaporator 106 and sensor T7 measures refrigeranttemperature exiting evaporator 106. Sensor T8 measures refrigeranttemperature entering evaporator 108 and sensor T9 measures refrigeranttemperature exiting evaporator 108. Sensor That1 measures temperature atlogic module 110 and sensor That2 measures temperature at logic module112.

Each temperature sensor generates a temperature signal which is suppliedto controller 120 and shown as Tin. The controller 120 adjusts theexpansion valves 114 and/or 116 in response to one or more of thetemperature signals to maintain the logic modules 110 and 112 at apredefined temperatures. Controller 120 controls expansion valves 114and/or 116 to obtain desired superheat values while maintaining eachlogic module at a desired temperature. Each logic module 110 and 112 maybe maintained at a different temperature or the same temperature, evenif each logic module has different heat loads.

Evaporators 106 and 108 may be connected to the refrigerant supply andrefrigerant return lines through quick disconnect connectors 130. Thecontrollable expansion valves 114 and 116 allow an evaporator to beremoved for maintenance or upgrade while the other evaporator, condenserand compressor continue to operate. For example, expansion valve 114 canbe closed and the refrigerant from evaporator 106 removed by the suctionof compressor 122. Evaporator 106 can then be removed for service,upgrade, etc.

FIG. 2 shows an alternate embodiment in which the refrigerant supplylines to evaporators 106 and 108 includes a secondary expansion valve134 and 136, respectively. Secondary expansion valves 134 and 136 may beimplemented using a fixed orifice valve or cap tube. This divides theexpansion of the refrigerant across two locations and allows theelectrically controlled expansion valves 114 and 116 to have enhancedgranularity. This also prevents the supply lines to evaporators 106 and108 from getting too cold.

The electrically controlled expansion valves 114 and 116 may be locatedin a modular refrigeration unit (MRU) that includes the condenser 104,compressor 122 and controller 120. The secondary expansion valve 134 and136 may be located close to evaporators 106 and 108, respectively. Thisaids in controlling the temperature of the logic modules, reduces spacerequired for insulating the supply lines to the evaporators and reduceswaste heat.

Although two evaporators are shown connected to one MRU (condenser,compressor, expansion valves and controller), it is understood that morethen two evaporators may be coupled to each MRU.

While the invention has been described with reference to exemplaryembodiments, it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted forelements thereof without departing from the scope of the invention. Inaddition, many modifications may be made to adapt a particular situationto the teachings of the invention without departing from the essentialscope thereof. Therefore, it is intended that the invention not belimited to the particular embodiments for carrying out this invention,but that the invention will include all embodiments falling within thescope of the appended claims.

1. A cooling system for cooling multiple logic modules, the coolingsystem comprising: a condenser; a first electrically controlledexpansion valve coupled to said condenser; a first evaporator coupled tosaid first electrically controlled expansion valve; a secondelectrically controlled expansion valve coupled to said condenser; asecond evaporator coupled to said second electrically controlledexpansion valve; a controller providing control signals to said firstelectrically controlled expansion valve and said second electricallycontrolled expansion valve to control operation of said firstelectrically controlled expansion valve and said second electricallycontrolled expansion valve; a compressor coupled to said firstevaporator, said second evaporator and said condenser.
 2. The coolingsystem of claim 1 wherein: said controller controls refrigerant flow andpressure drop in said first electrically controlled expansion valve andsaid second electrically controlled expansion valve.
 3. The coolingsystem of claim 1 further comprising: at least one temperature sensorproviding a temperature signal to said controller, said controllergenerating said control signals in response to said temperature signal.4. The cooling system of claim 3 wherein: said at least one temperaturesensor includes a plurality of temperature sensors.
 5. The coolingsystem of claim 4 wherein: said plurality of temperatures sensorsinclude a first temperature sensor providing a temperature signalindicative of temperature at one logic module and a second temperaturesensor providing a temperature signal indicative of refrigeranttemperature.
 6. The cooling system of claim 1 further comprising: afirst secondary expansion valve coupled between said first electricallycontrolled expansion valve and said first evaporator.
 7. The coolingsystem of claim 6 further comprising: a second secondary expansion valvecoupled between said second electrically controlled expansion valve andsaid second evaporator.
 8. The cooling system of claim 6 wherein: saidcondenser, said first electrically controlled expansion valve, saidsecond electrically controlled expansion valve, said compressor and saidcontroller are contained within a modular refrigeration unit, and saidfirst secondary expansion valve is positioned proximate to said firstevaporator.
 9. The cooling system of claim 1 wherein: said firstelectrically controlled expansion valve includes a stepper motor thatopens or closes an orifice in response to said control signals.